Double transfection improves small interfering RNA-induced thrombin receptor (PAR-1) gene silencing in DU 145 prostate cancer cells

Biocompatible hydroxyapatite-based nano vehicle bypasses viral transduction and enables sustained silencing of a pluripotency marker gene, demonstrating desired differentiation in mouse embryonic stem cells

BACKGROUND

Differentiation of pluripotent stem cells into desired lineages is the key aspect of regenerative medicine and cell-based therapy. Although RNA interference (RNAi) technology is exploited extensively for this, methods for long term silencing of the target genes leading to differentiation remain a challenge. Sustained knockdown of the target gene by RNAi is often inefficient as a result of low delivery efficiencies, protocol induced toxicity and safety concerns related to viral vectors. Earlier, we established octa-arginine functionalized hydroxyapatite nano vehicles (R8HNPs) for delivery of small interfering RNA (siRNA) against a pluripotency marker gene in mouse embryonic stem cells. Although we demonstrated excellent knockdown efficiency of the target gene, sustained gene silencing leading to differentiation was yet to be achieved.

METHODS

To establish a sustained non-viral gene silencing protocol using R8HNP, we investigated various methods of siRNA delivery: double delivery of adherent cells (Adh-D), suspension delivery followed by adherent delivery (Susp + Adh), single delivery in suspension (Susp-S) and multiple deliveries in suspension (Susp-R). Sustained knockdown of a pluripotent marker gene followed by differentiation was analysed by reverse transcriptase-PCR, fluoresence-activated cell sorting and immunofluorescence techniques. Impact on cell viability as a result of repeated exposure of the R8HNP was also tested.

RESULTS

Amongst the protocols tested, the most efficient knockdown of the target gene for a prolonged period of time was obtained by repeated suspension delivery of the R8HNP-siRNA conjugate. The long-term silencing of a pluripotency marker gene resulted in differentiation of R1 ESCs predominantly towards the extra embryonic and ectodermal lineages. Cells displayed excellent tolerance to repeated exposures of R8HNPs.

CONCLUSIONS

The results demonstrate that R8HNPs are promising, biocompatible, non-viral alternatives for prolonged gene silencing and obtaining differentiated cells for therapeutics.

Targeting F-actin stress fibers to suppress the dedifferentiated phenotype in chondrocytes

Actin is a central mediator of the chondrocyte phenotype. Monolayer expansion of articular chondrocytes on tissue culture polystyrene, for cell-based repair therapies, leads to chondrocyte dedifferentiation. During dedifferentiation, chondrocytes spread and filamentous (F-)actin reorganizes from a cortical to a stress fiber arrangement causing a reduction in cartilage matrix expression and an increase in fibroblastic matrix and contractile molecule expression. While the downstream mechanisms regulating chondrocyte molecular expression by alterations in F-actin organization have become elucidated, the critical upstream regulators of F-actin networks in chondrocytes are not completely known. Tropomyosin (TPM) and the RhoGTPases are known regulators of F-actin networks. The main purpose of this study is to elucidate the regulation of passaged chondrocyte F-actin stress fiber networks and cell phenotype by the specific TPM, TPM3.1, and the RhoGTPase, CDC42. Our results demonstrated that TPM3.1 associates with cortical F-actin and stress fiber F-actin in primary and passaged chondrocytes, respectively. In passaged cells, we found that pharmacological TPM3.1 inhibition or siRNA knockdown causes F-actin reorganization from stress fibers back to cortical F-actin and causes an increase in G/F-actin. CDC42 inhibition also causes formation of cortical F-actin. However, pharmacological CDC42 inhibition, but not TPM3.1 inhibition, leads to the re-association of TPM3.1 with cortical F-actin. Both TPM3.1 and CDC42 inhibition, as well as TPM3.1 knockdown, reduces nuclear localization of myocardin related transcription factor, which suppresses dedifferentiated molecule expression. We confirmed that TPM3.1 or CDC42 inhibition partially redifferentiates passaged cells by reducing fibroblast matrix and contractile expression, and increasing chondrogenic SOX9 expression. A further understanding on the regulation of F-actin in passaged cells may lead into new insights to stimulate cartilage matrix expression in cells for regenerative therapies.

Cell surface expression of Ribophorin I, an endoplasmic reticulum protein, over different cell types

Ribophorin-1 serves as one of the subunits of the oligosaccharyltransferase (OST) complex located in the endoplasmic reticulum (ER). Until now, RPN-1 was considered an ER protein. However, our findings reveal that a minor fraction of RPN-1 escapes from the lumen of the ER and is ectopically expressed on the surface of different cell lines. The precise mechanism of protein translocation is unknown. The expression of RPN-1 was demonstrated through the isolation of membrane proteins using surface biotinylation and sucrose density gradient techniques. The confirmation of RPN-1 was obtained through surface staining using a specific antibody, revealing its expression on various cell lines. Additionally, we examined the expression of RPN-1 in different populations of PBMCs and observed a differential regulation of RPN-1 within PBMC subpopulations. Notably, there was a significant expression of RPN-1 on monocytes and B cells, but there was little to no population of T cells expressing RPN-1. We confirmed the expression of RPN-1 on THP-1, U937, and Jurkat cells. We also confirmed their surface expression through si-RNA knockdown. Our study shows RPN-1 expression on various cell surfaces, suggesting varied regulation among cell types. In the future, we may uncover its roles in immune function, signaling, and differentiation/proliferation.

Linderapyrone analogue LPD-01 as a cancer treatment agent by targeting importin7

The Wnt/β-catenin signaling pathway plays important roles in several cancer cells, including cell proliferation and development. We previously succeeded in synthesizing a small molecule compound inhibiting the Wnt/β-catenin signaling pathway, named LPD-01 (1), and 1 inhibited the growth of human colorectal cancer (HT-29) cells. In this study, we revealed that 1 inhibits the growth of HT-29 cells stronger than that of another human colorectal cancer (SW480) cells. Therefore, we have attempted to identify the target proteins of 1 in HT-29 cells. Firstly, we investigated the effect on the expression levels of the Wnt/β-catenin signaling pathway-related proteins. As a result, 1 inhibited the expression of target proteins of Wnt/β-catenin signaling pathway (c-Myc and Survivin) and their genes, whereas the amount of transcriptional co-activator (β-catenin) was not decreased, suggesting that 1 inhibited the Wnt/β-catenin signaling pathway without affecting β-catenin. Next, we investigated the target proteins of 1 using magnetic FG beads. Chemical pull-down assay combined with mass spectrometry suggested that 1 directly binds to importin7. As expected, 1 inhibited the nuclear translocation of importin7 cargoes such as Smad2 and Smad3 in TGF-β-stimulated HT-29 cells. In addition, the knockdown of importin7 by siRNA reduced the expression of target genes of Wnt/β-catenin signaling pathway. These results suggest that importin7 is one of the target proteins of 1 for inhibition of the Wnt/β-catenin signaling pathway.

In situ transient transfection of 3D cell cultures and tissues, a promising tool for tissue engineering and gene therapy

Various research fields use the transfection of mammalian cells with genetic material to induce the expression of a target transgene or gene silencing. It is a tool widely used in biological research, bioproduction, and therapy. Current transfection protocols are usually performed on 2D adherent cells or suspension cultures. The important rise of new gene therapies and regenerative medicine in the last decade raises the need for new tools to empower the in situ transfection of tissues and 3D cell cultures. This review will present novel in situ transfection methods based on a chemical or physical non-viral transfection of cells in tissues and 3D cultures, discuss the advantages and remaining gaps, and propose future developments and applications.

Protease-activated receptor 1 inhibition protects mice against thrombin-dependent respiratory syncytial virus and human metapneumovirus infections

BACKGROUND AND PURPOSE

Protease-activated receptor 1 (PAR1) has been demonstrated to be involved in the pathogenesis of viral diseases. However, its role remains controversial. The goal of our study was to investigate the contribution of PAR1 to respiratory syncytial virus (RSV) and human metapneumovirus (hMPV) infections.

EXPERIMENTAL APPROACH

Pharmacological approaches were used to investigate the role of PAR1 during RSV and hMPV infection, in vitro using epithelial A549 cells and in vivo using a mouse model of virus infection.

KEY RESULTS

In vitro, the PAR1 antagonist RWJ-56110 reduced the replication of RSV and hMPV in A549 cells. In agreement with these results, RWJ-56110-treated mice were protected against RSV and hMPV infections, as indicated by less weight loss and mortality. This protective effect in mice correlated with decreased lung viral replication and inflammation. In contrast, hMPV-infected mice treated with the PAR1 agonist TFLLR-NH₂ showed increased mortality, as compared to infected mice, which were left untreated. Thrombin generation was shown to occur downstream of PAR1 activation in infected mice via tissue factor exposure as part of the inflammatory response, and thrombin inhibition by argatroban reduced the pathogenicity of the infection with no additive effect to that induced by PAR1 inhibition.

CONCLUSION AND IMPLICATIONS

These data show that PAR1 plays a detrimental role during RSV and hMPV infections in mice via, at least, a thrombin-dependent mechanism. Thus, the use of PAR1 antagonists and thrombin inhibitors may have potential as a novel approach for the treatment of RSV and hMPV infections.

Protein Carbonylation of an Amino Acid Residue of the Na/K-ATPase α1 Subunit Determines Na/K-ATPase Signaling and Sodium Transport in Renal Proximal Tubular Cells

BACKGROUND

We have demonstrated that cardiotonic steroids, such as ouabain, signaling through the Na/K-ATPase, regulate sodium reabsorption in the renal proximal tubule. By direct carbonylation modification of the Pro222 residue in the actuator (A) domain of pig Na/K-ATPase α1 subunit, reactive oxygen species are required for ouabain-stimulated Na/K-ATPase/c-Src signaling and subsequent regulation of active transepithelial (22)Na(+) transport. In the present study we sought to determine the functional role of Pro222 carbonylation in Na/K-ATPase signaling and sodium handling.

METHODS AND RESULTS

Stable pig α1 knockdown LLC-PK1-originated PY-17 cells were rescued by expressing wild-type rat α1 and rat α1 with a single mutation of Pro224 (corresponding to pig Pro222) to Ala. This mutation does not affect ouabain-induced inhibition of Na/K-ATPase activity, but abolishes the effects of ouabain on Na/K-ATPase/c-Src signaling, protein carbonylation, Na/K-ATPase endocytosis, and active transepithelial (22)Na(+) transport.

CONCLUSIONS

Direct carbonylation modification of Pro224 in the rat α1 subunit determines ouabain-mediated Na/K-ATPase signal transduction and subsequent regulation of renal proximal tubule sodium transport.

Thrombin receptor PAR-1 activation on endothelial progenitor cells enhances chemotaxis-associated genes expression and leukocyte recruitment by a COX-2-dependent mechanism

BACKGROUND

Endothelial colony forming cells (ECFC) represent a subpopulation of endothelial progenitor cells involved in endothelial repair. The activation of procoagulant mechanisms associated with the vascular wall's inflammatory responses to injury plays a crucial role in the induction and progression of atherosclerosis. However, little is known about ECFC proinflammatory potential.

AIMS

To explore the role of the thrombin receptor PAR-1 proinflammatory effects on ECFC chemotaxis/recruitment capacity.

METHODS AND RESULTS

The expression of 30 genes known to be associated with inflammation and chemotaxis was quantified in ECFC by real-time qPCR. PAR-1 activation with the SFLLRN peptide (PAR-1-ap) resulted in a significant increase in nine chemotaxis-associated genes expression, including CCL2 and CCL3 whose receptors are present on ECFC. Furthermore, COX-2 expression was found to be dramatically up-regulated consequently to PAR-1 activation. COX-2 silencing with the specific COX-2-siRNA also triggered down-regulation of the nine target genes. Conditioned media (c.m.) from control-siRNA- and COX-2-siRNA-transfected ECFC, stimulated or not with PAR-1-ap, were produced and tested on ECFC capacity to recruit leukocytes in vitro as well in the muscle of ischemic hindlimb in a preclinical model. The capacity of the c.m. from ECFC stimulated with PAR-1-ap to recruit leukocytes was abrogated when COX-2 gene expression was silenced in vitro (in terms of U937 cells migration and adhesion to endothelial cells) as well as in vivo. Finally, the postnatal vasculogenic stem cell derived from infantile hemangioma tumor (HemSC) incubated with PAR-1-ap increased leukocyte recruitment in Matrigel(®) implant.

CONCLUSIONS

PAR-1 activation in ECFC increases chemotactic gene expression and leukocyte recruitment at ischemic sites through a COX-2-dependent mechanism.

Protease activated receptor-1 mediates cytotoxicity during ischemia using in vivo and in vitro models

Protease activated receptors (PARs) populate neurons and astrocytes in the brain. The serine protease thrombin, which activates PAR-1 during the first hours after stroke, appears to be associated with the cytotoxicity. Thrombin antagonists and PAR-1 inhibitors have been correlated with reduced cell death and behavioral protection after stroke, but no data yet support a mechanistic link between PAR-1 action and benefit. We sought to establish the essential role of PAR-1 in mediating ischemic damage. Using a short hairpin mRNA packaged with green fluorescent protein in a lentivirus vector, we knocked downPAR-1 in the medial caudate nucleus prior to rat middle cerebral artery occlusion (MCAo) and in rat neurons prior to oxygen-glucose deprivation. We also compared aged PAR-1 knockout mice with aged PAR-3, PAR-4 mice and young wild-type mice in a standard MCAo model. Silencing PAR-1 significantly reduced neurological deficits, reduced endothelial barrier leakage, and decreased neuronal degeneration in vivo during MCAo. PAR-1 knock-down in the ischemic medial caudate allowed cells to survive the ischemic injury; infected cells were negative for terminal deoxynucleotidyl transferase mediated dUTP Nick End Labeling (TUNEL) and c-Fos injury markers. Primary cultured neurons infected with PAR-1 short hairpin ribonucleic acid (shRNA) showed increased neuroprotection during hypoxic/aglycemic conditions with or without added thrombin. The aged PAR-1 knockout mice showed decreased infarction and vascular disruption compared to aged controls or young wild types. We demonstrated an essential role for PAR-1 during ischemia. Silencing or removing PAR-1 significantly protected neurons and astrocytes. Further development of agents that act at PAR-1 or its downstream pathways could yield powerful stroke therapy.

Involvement of reactive oxygen species in a feed-forward mechanism of Na/K-ATPase-mediated signaling transduction

Cardiotonic steroids (such as ouabain) signaling through Na/K-ATPase regulate sodium reabsorption in the renal proximal tubule. We report here that reactive oxygen species are required to initiate ouabain-stimulated Na/K-ATPase·c-Src signaling. Pretreatment with the antioxidant N-acetyl-L-cysteine prevented ouabain-stimulated Na/K-ATPase·c-Src signaling, protein carbonylation, redistribution of Na/K-ATPase and sodium/proton exchanger isoform 3, and inhibition of active transepithelial (22)Na(+) transport. Disruption of the Na/K-ATPase·c-Src signaling complex attenuated ouabain-stimulated protein carbonylation. Ouabain-stimulated protein carbonylation is reversed after removal of ouabain, and this reversibility is largely independent of de novo protein synthesis and degradation by either the lysosome or the proteasome pathways. Furthermore, ouabain stimulated direct carbonylation of two amino acid residues in the actuator domain of the Na/K-ATPase α1 subunit. Taken together, the data indicate that carbonylation modification of the Na/K-ATPase α1 subunit is involved in a feed-forward mechanism of regulation of ouabain-mediated renal proximal tubule Na/K-ATPase signal transduction and subsequent sodium transport.

Protein kinase A regulates MYC protein through transcriptional and post-translational mechanisms in a catalytic subunit isoform-specific manner

MYC levels are tightly regulated in cells, and deregulation is associated with many cancers. In this report, we describe the existence of a MYC-protein kinase A (PKA)-polo-like kinase 1 (PLK1) signaling loop in cells. We report that sequential MYC phosphorylation by PKA and PLK1 protects MYC from proteasome-mediated degradation. Interestingly, short term pan-PKA inhibition diminishes MYC level, whereas prolonged PKA catalytic subunit α (PKACα) knockdown, but not PKA catalytic subunit β (PKACβ) knockdown, increases MYC. We show that the short term effect of pan-PKA inhibition on MYC is post-translational and the PKACα-specific long term effect on MYC is transcriptional. These data also reveal distinct functional roles among PKA catalytic isoforms in MYC regulation. We attribute this effect to differential phosphorylation selectivity among PKA catalytic subunits, which we demonstrate for multiple substrates. Further, we also show that MYC up-regulates PKACβ, transcriptionally forming a proximate positive feedback loop. These results establish PKA as a regulator of MYC and highlight the distinct biological roles of the different PKA catalytic subunits.

siRNA-mediated silence of protease-activated receptor-1 minimizes ischemic injury of cerebral cortex through HSP70 and MAP2

Cerebral ischemic stroke is a prevalent disease in senior individuals. The anticoagulation and thrombolysis to recover blood supply as well as the diminution of neural excitotoxicity to protect brain cells have not shown to fully improve stroke patients. The comprehensive mechanisms and medication specificity remain to be addressed. The silence of specific mRNAs by RNA interference provides revenues for such goals. We examined whether the silence of protease-activated receptor-1 (PAR-1) by siRNA protects brain tissues from ischemic injury. In three groups of Wistar rats, their lateral ventricles received the injections of lentiviral vectors carrying siRNA for PAR1, small RNA in mismatching PAR1 or saline. A week after the injections, these rats were treated by one side of middle cerebral artery occlusion (MCAO). The scores of neurological deficits, the volume of ischemic infarction and the expressions of PAR-1, HSP-70 and MAP-2 were measured in 24h of MCAO. Our results show that the silence of PAR-1 significantly reduces neurological deficits and infarction volume, as well as elevates HSP-70 and MAP-2 expressions. Thus, the knock-down of PAR1 minimizes the ischemic impairments of cerebral cortex via HSP70 and MAP-2 pathways.

Cell contact-dependent functional selectivity of β2-adrenergic receptor ligands in stimulating cAMP accumulation and extracellular signal-regulated kinase phosphorylation

Activation of β(2)-adrenegic receptor (β(2)-AR) leads to an increase in intracellular cAMP and activation of ERK. These two signals are activated by the interaction of the receptor with different transducer partners. We showed that the intrinsic activities of β(2)-AR ligands for stimulating cAMP production and ERK phosphorylation responses in HEK-293 cells were not correlated. The lack of correlation resulted mainly from the discrepancy between the intrinsic activities of two groups of ligands for these two responses: The first group consisted of clenbuterol, cimaterol, procaterol, and terbutaline which acted as full agonists for cAMP production but displayed very weak effect on ERK phosphorylation. The second group comprised adrenaline and noradrenaline which displayed higher intrinsic activity for the ERK phosphorylation than for the cAMP response. Thus, both groups behaved as functionally selective ligands. The functional selectivity of the first group was observable only in adherent cells when confluence was approximately 100%. When cell-cell contact was minimized either by decreasing the density of the adherent cells or by bringing the cells into suspension, the first group of ligands gained the ability to stimulate ERK phosphorylation without a change in their effect on cAMP production. In contrast, selectivity of the second group was independent of the adherence state of the cells. Our results show that the inherent "bias" of ligands in coupling a G protein-coupled receptor to different transducers may not always be revealed as functional selectivity when there is a "cross-talk" between the signaling pathways activated by the same receptor.

Effect of RNAi-induced down regulation of nuclear factor kappa-B p65 on acute monocytic leukemia THP-1 cells in vitro and vivo

NF-κB p65 is found constitutively active in acute monocytic leukemia, and has been considered an important factor for poor prognosis. Therefore, develop specifically target p65 inhibitors will be substantial interest. Until now, although several p65 inhibitors are currently in preclinical and clinical development, none of them are targeting. In this study, siRNA targeting p65 was introduced into the acute monocytic leukemia cell line THP-1 and THP-1 xenograft tumors in nude mice, and then, we measured p65 mRNA and protein levels by real-time RT-PCR and Western blotting, and levels of related protein cyclin D1, Bc1-2, and SMRT by Western blotting. We also investigated the cell cycle and apoptosis via FCM, and cell proliferation by Cell Counting Kit-8 assay. We found that p65 siRNA could effectively reduce the p65 mRNA and protein expression, arrest cells in G0/G1 phase, inhibit the proliferation and increase the apoptosis of THP-1 cells, and intratumoral injection of p65 siRNA could suppress tumor growth in nude mice. We also found that when down regulation of p65, the expression of cyclin D1 and Bc1-2 decreased, and the expression of SMRT increased in vitro and vivo. All these findings suggest that NF-κB p65 maybe an attractive candidate for the therapeutic targeting of acute monocytic leukemia.

Paclitaxel tumor-priming enhances siRNA delivery and transfection in 3-dimensional tumor cultures

The clinical development of siRNA cancer therapeutics is limited by the poor interstitial transport and inefficient transfection in solid tumors. We have shown that paclitaxel pretreatment, by inducing apoptosis, causes expansion of the interstitial space and thereby improves nanoparticle delivery and transport in tumor interstitium (referred to as paclitaxel tumor priming) and efficacy of nanomedicines in tumor-bearing animals. The present study evaluated whether paclitaxel tumor priming improves the delivery and transfection of siRNA in 2- and 3-dimensional cultures of human oropharyngeal carcinoma FaDu cells. We used the fluorescent siGLO and confocal microcopy to monitor transport, and used survivin siRNA and immunostaining and immunoblotting to monitor transfection. Survivin is a chemoresistance gene/protein, inducible by chemotherapy. siRNA was loaded in cationic liposomes. The results showed that pretreatment with 50-200 nM paclitaxel (24 or 48 h before siRNA) enhanced the total uptake of siGLO into monolayers (∼15%, p < 0.05), and the depth of penetration into 3-dimensional spheroids and tumor fragment histocultures (2.1- to 2.5-times greater area under the penetration-depth curve). In both monolayer cells and histocultures, paclitaxel pretreatment induced survivin upregulation (p < 0.05). Survivin siRNA alone decreased the survivin levels in a dose-dependent manner, and applying survivin siRNA after paclitaxel pretreatment completely abolished the paclitaxel-induced survivin increases. These findings indicate that paclitaxel tumor priming did not compromise the siRNA functionality. In summary, paclitaxel tumor priming improved the penetration, transfection and functionality of siRNA in tumors, thus offering a promising and practical means to develop chemo-siRNA cancer gene therapy.

Down-regulation of glial fibrillary acidic protein and vimentin by RNA interference improves acute urinary dysfunction associated with spinal cord injury in rats

In spinal cord injury, glial scarring, a result of overexpressed intermediate filament (IF) proteins including glial fibrillary acidic protein (GFAP) and vimentin, is one of the largest obstacles in axonal regeneration. We postulated that specific suppression of IF proteins in the injured CNS might inhibit the excessive reactivity of astrocytes and thereby suppress glial scarring. siRNAs targeting GFAP and vimentin were transfected separately into C6 glioma cells and rat hippocampal astrocytes. These siRNAs suppressed both biphasic elements of each IF proteins: the ordinarily expressed elements having slow turnover and the immediately inducible elements stimulated by tumor necrosis factor-a (TNF-α). Moreover, adenovirus vectors expressing GFAP or vimentin siRNAs suppressed the proliferation of C6 glioma cells on days 3-9 after infection. Finally, each siRNA mixed with atelocollagen was applied together to the contused thoracic spines of spinal cord injury (SCI) model rats. The introduction of GFAP and vimentin siRNAs prevented the overexpression of IF proteins in the injured lesion (namely, in the white matter surrounding the long tract where the lateral funiculus exists and in the gray matter near the anterior horn neurons). Furthermore, the starting date of spontaneous voiding was significantly accelerated by application of GFAP and vimentin siRNAs. The inhibition of undesirable glial activity surrounding micturition-related pathways improved acute urinary dysfunction due to neurogenic bladder. In conclusion, the down-regulation of IF proteins by RNAi suppresses the overproliferation of reactive astrocytes and thereby might be an effective treatment for spinal cord injury.

Protease-activated receptor-1 (PAR-1) promotes the motility of human melanomas and is associated to their metastatic phenotype

Protease-activated receptor-1 (PAR-1) is a unique G-protein-coupled receptor belonging to the protease-activated receptor family. Its activation leads to downstream signaling events that launch a variety of cellular responses related to tumor progression. PAR-1 expression has been associated to a variety of human cancers, and our previous studies reveal a high PAR-1 expression in melanoma specimens as compared to common nevi. In the present study, we investigated the contribution of PAR-1 to the malignant phenotype of human melanoma cell lines obtained from cutaneous primary lesions, capable of different metastatic behaviors in the patients from which they have been derived. We found that melanoma cells isolated from lesions giving rise to metastases in patients (WM115, WM278A, WM1361A, WM983A), had higher PAR-1 mRNA and protein expression, as compared to those obtained from lesions that did not develop metastatic disease (WM793, WM35). The cells isolated from metastatic primary lesions were able to colonize the lungs of immunodeficient SCID mice while those isolated from non-metastatic lesions were not. Additionally, cells expressing elevated PAR-1 had higher migratory and invasive abilities than those holding minimal PAR-1 expression. The migration and invasion capabilities of the melanoma cells expressing high PAR-1 were hampered by genetic and pharmacological interventions. The reduction of PAR-1 expression by siRNA and the inhibition of PAR-1 function by the SCH79797 specific antagonist significantly decreased the melanoma cell motility and invasiveness, down to an extent similar to that of the non-metastatic and low PAR-1 expressing cells. Our results provide strong evidence supporting the implication of PAR-1 in the malignant progression of human melanoma.

Prostate-specific kallikreins-2 and -4 enhance the proliferation of DU-145 prostate cancer cells through protease-activated receptors-1 and -2

A major characteristic of prostate cancer is the elevation of serum levels of prostate-specific antigen (hK3) and hK2, which are tumor markers that correlate with advancing stages of disease. Including hK4, these three kallikrein serine proteases are almost exclusively produced by the prostate. Prostate cancer cells have been recently shown to overexpress protease-activated receptors (PAR), which can be potentially activated by kallikreins and can regulate tumor growth. Here, we show that recombinant hK2 and hK4 activate ERK1/2 signaling of DU-145, PC-3, and LNCaP prostate cancer cells, which express both PAR1 and PAR2. These kallikreins also stimulate the proliferation of DU-145 cells. Pretreatment of hK2 and hK4 with the serine protease inhibitor, aprotinin, blocks the responses in DU-145 cells, and small interfering RNA against PAR1 and PAR2 also inhibits ERK1/2 signaling. To determine which PAR is activated by hK2 and hK4, a cell line that expresses a single PAR, a PAR1 knockout mouse lung fibroblast cell line transfected with PAR1 (KOLF-PAR1) or PAR2 (KOLF-PAR2) was used. hK4 activates both PAR1 and PAR2, whereas hK2 activates PAR2. hK4 generates more phosphorylated ERK1/2 than hK2. These data indicate that prostatic kallikreins (hK2 and hK4) directly stimulate prostate cancer cell proliferation through PAR1 and/or PAR2 and may be potentially important targets for future drug therapy for prostate cancer.

Interleukin 8 is differently expressed and modulated by PAR-1 activation in early and late endothelial progenitor cells

The proinflammatory chemokine interleukin 8 exerts potent angiogenic effects on endothelial cells by interacting with its receptors CXCR1 and CXCR2. As thrombin is also a potent inflammatory factor, and as endothelial progenitor cells (EPC) express functional PAR-1 thrombin receptor, we examined whether PAR-1 stimulation interferes with the IL-8 pathway in EPC. EPC were obtained from adult blood (AB) and cord blood (CB). The effect of PAR-1 stimulation by the peptide SFLLRN on IL-8, CXCR1 and CXCR2 expression was examined by RTQ-PCR and at the protein level in AB and CB late EPC and in AB early EPC. Specific siRNA was used to knock down PAR-1 expression. The IL-8 gene was expressed strongly in AB early EPC and moderately in late EPC. In contrast, CXCR1 and CXCR2 gene expression was restricted to AB early EPC. The IL-8 level in AB early EPC conditioned medium was high in basal conditions and did not change after PAR-1 activation. By contrast, IL-8 secretion by late EPC was low in basal conditions and strongly up-regulated upon PAR-1 activation. PAR-1 activation induced a number of genes involved in activating protein-1 (AP-1) and nuclear factor (NF)-kappaB pathways. Conditioned medium of PAR-1-activated late EPC enhanced the migratory potential of early EPC, and this effect was abrogated by blocking IL-8. Target-specific siRNA-induced PAR-1 knockdown, and fully inhibited PAR-1-induced IL-8 synthesis. In conclusion, PAR-1 activation induces IL-8 synthesis by late EPC. This could potentially enhance cooperation between late and early EPC during neovascularization, through a paracrine effect.

Protease-activated receptor-1 upregulates fibroblast growth factor 7 in stroma of benign prostatic hyperplasia

BACKGROUND

Benign prostatic hyperplasia (BPH) is characterized by abnormal epithelial and stromal proliferation causing urinary obstruction. Prostate growth is regulated by a variety of growth factors secreted from the stroma, including fibroblast growth factor 7 (FGF-7), a potent epithelial-specific growth factor which is increased in hyperplastic prostate. However, the mediator(s) of FGF-7 over-expression is unclear. Protease-activated receptor-1 (PAR-1) is a G-protein coupled receptor known to induce multiple biological processes, but its effect on BPH pathogenesis is mostly unknown. The aim of this study was to investigate the role of PAR-1 as a mediator of BPH development.

METHODS

PAR-1 expression was investigated in BPH and normal prostate tissues by immunohistochemistry. Prostate stromal cells were isolated from BPH specimens, cultured and immunohistochemically characterized. Cultured stromal cells were stimulated with PAR-1 agonists, and extracellular-signal regulated kinase (ERK1/2) activation and cell proliferation were examined. PAR-1 mediated FGF-7 production by cultured stromal cells was assessed by RT-PCR and immunoassays, and verified by small interfering RNA (siRNA).

RESULTS

PAR-1 expression was increased in BPH stroma. In stromal cells isolated from BPH tissues, PAR-1 agonists activated ERK1/2 in a time- and concentration-dependent manner and with resultant enhanced cell proliferation. Pertussis toxin-sensitive G protein/(betagamma-subunits)-phosphatidylinositol 3-kinase and protein kinase C pathways were involved in ERK1/2 phosphorylation. PAR-1 activation strikingly induced FGF-7 production from cultured stromal cells mediated predominantly via ERK1/2 signaling pathway, and PAR-1 siRNA decreased the elicited FGF-7 upregulation.

CONCLUSIONS

The expression and function of PAR-1 in BPH stroma indicate PAR-1 may play important roles in BPH pathogenesis.

Mechanisms of resistance and adaptation to thapsigargin in androgen-independent prostate cancer PC3 and DU145 cells

Cells with increasing resistance to the sarcoplasmic/endoplasmic reticulum Ca(2+)-ATPase (SERCA) inhibitor thapsigargin (TG), ranging from 60-fold (PC3/TG(10) cells) to 1350-fold (PC3/TG(2000) cells), were derived from PC3 cells. SERCA2 is overexpressed in all PC3/TG cells but retains sensitivity to TG. siRNA-mediated downregulation of SERCA completely or partially reverses TG resistance in PC3/TG(10) or PC3/TG(2000) cells, respectively; thus SERCA overexpression mediates resistance in PC3/TG(10) cells but is not the only resistance mechanism in PC3/TG(2000) cells. By contrast, SERCA is not overexpressed in TG-resistant DU145/TG cells derived from DU145 cells. DU145/TG cells retain resistance while in PC3/TG cells resistance decreases upon removal of TG selection. The transport proteins PGP/BCRP/MRP1 and anti-apoptotic proteins Bcl2/Bcl(XL) are not involved in mediating resistance in either cell line. PARP and caspase 3 cleavage in response to other drugs demonstrate that the apoptotic pathways tested remain intact in these cells. Further, no cross-resistance occurs to other drugs. Thus, novel TG-specific resistance mechanisms are recruited by these cancer cells.

Gene manipulation through the use of small interfering RNA (siRNA): from in vitro to in vivo applications

The conventional approach to investigate genotype-phenotype relationships has been the generation of gene targeted murine strains. However, the emergence of RNAi technologies has opened the possibility of much more rapid (and indeed more cost effective) genetic manipulation in vivo at the level of the transcriptome. Successful application of RNAi in vivo depends on intracellular targeted delivery of siRNA/shRNA molecules for efficient knockdown of the desired gene. In this review, we discuss the rationale and different strategies of using siRNA/shRNA for accomplishing the silencing of targeted genes in a spatial and /or temporally regulated manner. We also summarise the steps involved in extending these approaches to in vivo applications, with a specific focus upon the development of silencing in the mouse.

NKX3.1 is regulated by protein kinase CK2 in prostate tumor cells

Diminished expression of NKX3.1 is associated with prostate cancer progression in humans, and in mice, loss of nkx3.1 leads to epithelial cell proliferation and altered gene expression patterns. The NKX3.1 amino acid sequence includes multiple potential phosphoacceptor sites for protein kinase CK2. To investigate posttranslational regulation of NKX3.1, phosphorylation of NKX3.1 by CK2 was studied. In vitro kinase assays followed by mass spectrometric analyses demonstrated that CK2 phosphorylated recombinant NKX3.1 on Thr89 and Thr93. Blocking CK2 activity in LNCaP cells with apigenin or 5,6-dichlorobenzimidazole riboside led to a rapid decrease in NKX3.1 accumulation that was rescued by proteasome inhibition. Replacing Thr89 and Thr93 with alanines decreased NKX3.1 stability in vivo. Small interfering RNA knockdown of CK2alpha' but not CK2alpha also led to a decrease in NKX3.1 steady-state level. In-gel kinase assays and Western blot analyses using fractionated extracts of LNCaP cells demonstrated that free CK2alpha' could phosphorylate recombinant human and mouse NKX3.1, whereas CK2alpha' liberated from the holoenzyme could not. These data establish CK2 as a regulator of NKX3.1 in prostate tumor cells and provide evidence for functionally distinct pools of CK2alpha' in LNCaP cells.

Thrombin/thrombin receptor (PAR-1)-mediated induction of IL-8 and VEGF expression in prostate cancer cells

Interleukin 8 (IL-8) and vascular endothelial growth factor (VEGF) are two cytokines promoting prostate tumor growth and angiogenesis. The main coagulation protease thrombin may modulate the malignant phenotype of prostate cancer cells via its cellular receptor(s). We aimed to investigate the effects of thrombin on IL-8 and VEGF expression in DU 145 prostate cancer cells. Thrombin induced the expression and secretion of IL-8 and VEGF, with more pronounced effects on IL-8. Target-specific siRNA-induced protease-activated receptor 1 (PAR-1) knockdown completely neutralized thrombin-enhanced cytokine secretion, demonstrating the essential role of PAR-1. Inhibitors of either extracellular signal-regulating kinase (ERK) or phosphatidylinositol 3-kinase (PI3K) partly reversed the thrombin-induced cytokine expression, suggesting that both ERK and PI3K kinase pathways may be involved in IL-8 and VEGF expression. The results suggest that the thrombin/PAR-1 system upregulates cytokines in prostate cancer cells which in turn may contribute to the progression of prostate cancer.

Ovarian cancer, the coagulation pathway, and inflammation

Epithelial ovarian cancer (EOC) represents the most frequent cause of death in the United States from a cancer involving the female genital tract. Contributing to the overall poor outcome in EOC patients, are the metastases to the peritoneum and stroma that are common in this cancer. In one study, cDNA microarray analysis was performed on fresh tissue to profile gene expression in patients with EOC. This study showed a number of genes with significantly altered expression in the pelvic peritoneum and stroma, and in the vicinity of EOC implants. These genes included those encoding coagulation factors and regulatory proteins in the coagulation cascade and genes encoding proteins associated with inflammatory responses. In addition to promoting the formation of blood clots, coagulation factors exhibit many other biologic functions as well as tumorigenic functions, the later including tumor cell proliferation, angiogenesis, invasion, and metastasis. Coagulation pathway proteins involved in tumorigenesis consist of factor II (thrombin), thrombin receptor (protease-activated receptors), factor III (tissue factor), factor VII, factor X and factor I (fibrinogen), and fibrin and factor XIII. In a recent study we conducted, we found that factor XII, factor XI, and several coagulation regulatory proteins, including heparin cofactor-II and epithelial protein C receptor (EPCR), were also upregulated in the peritoneum of EOC. In this review, we summarize evidence in support of a role for these factors in promoting tumor cell progression and the formation of ascites. We also discuss the different roles of coagulation factor pathways in the tumor and peritumoral microenvironments as they relate to angiogenesis, proliferation, invasion, and metastasis. Since inflammatory responses are another characteristic of the peritoneum in EOC, we also discuss the linkage between the coagulation cascade and the cytokines/chemokines involved in inflammation. Interleukin-8, which is considered an important chemokine associated with tumor progression, appears to be a linkage point for coagulation and inflammation in malignancy. Lastly, we review findings regarding the inflammatory process yielded by certain clinical trials of agents that target members of the coagulation cascade in the treatment of cancer. Current data suggest that disrupting certain elements of the coagulation and inflammation processes in the tumor microenvironment could be a new biologic approach to cancer therapeutics.